Floating roof tank warning device



y 4, 1954 H. A. QUIST 2,677,816

FLOATING ROOF TANK WARNING DEVICE Filed March 25. 1952 INVENTOR. 52HAROLD A.QUIST ATTORNEYS 2 Sheets-Sheet l May 4, 1954 H. A. QUIST2,677,816

FLOATING ROOF TANK WARNING DEVICE Filed March 25. 1952 2 Sheets-Sheet 2lo 64 IO 20 l8 K: 2 l2 76 l8 82 :1 "l q & Y8

Fig. 6

VENTOR.

HARO .QUIST -BY ATTORNEYS Patented May 4, 1954 FLOATING ROOF TANKWARNING DEVICE Harold A. Quist, Swarth Oil Company, of New Jersey more,Pa., assignor to Sun Philadelphia, Pa., a corporation Application March25, 1952, Serial N 0. 278,337 5 Claims. (Cl. 340-244) This inventionrelates in general to floating roof tanks as used for storage of liquidsand more particularly to means for indicating the failure of such roofsto operate properly.

Among the many possible reasons a floating roof in a liquid storage tankmay fail to operate properly, there are four of primary importance. Theyare:

a. Sinking in the stored liquid because of leaks, snow load, freezing,wind pressure.

12. Lifting above the top of the tank because of overflow of the liquid.

0. Accumulation of explosive gases beneath the roof after more than themaximum of liquid is withdrawn from the storage vessel.

[2. Sticking at one position in the storage tank because of icing,gumming or obstructions caught in the perimeter seal.

It will be recognized that any of these conditions, in addition tocreating a dangerous situa-,

tion, will give an erroneous measure of the stored contents. Except forthe extremes of tank volumes either maximum or minimum, there is noevidence of any unusual condition by mere observance of the roofposition or of any visible indicator connected thereto. Where the roofis stuck or is sinking in the liquid it will look and be normallyindicated as properly functioning.

The primary concern in the past, over the conditions enumerated here,has been limited to signalling the position of the floating roof onlyfor the overflow condition. Although this is one of the greatestdangers, its correction does not elimihate the other equally gravesituations listed above. It is an object of vide a floating roof tankwith a single means equally responsive to these primary causes offloating roof failure to operate desired signals.

In accordance with the present invention, a float operated lever arm ispositioned to extend through the floating roof element and engage alatch adjacent the top thereof. In order to operate the device when thefloating roof reaches the minimum allowable liquid depth, the lever armis extended a predetermined distance below the roofs liquid contactsurface. The latch is connected to a cable which is guided over the sideof the storage tank and positioned to suspend an electrical connectingelement. In the form illustrated, a simple depth indicator is mountedalongside the storage tank and shows the liquid depth in cooperationwith the electrical connecting element. The illustrated form of thedevice indicates the operating condition of the floating roof at thesite of the storage tank in addition to this invention toprotransmitting a signal of failure to any selected location removedfrom the tank.

For a more complete understanding of the nature and scope of theinvention wherein the above noted object and others will be evident,reference is made to the following detailed description read inconnection with the accompanying drawing in which:

Figure 1 is an elevational view, partly broken away showing the devicein operating arrangement.

Figures 2, 3, 4, and 5 are sectional elevational views of the floatmechanism in four operating positions.

Figure 6 i a sectional plan view of Figure 2 taken on line 6-6.

Referring to Figure l, the float mechanism generally indicated by thenumeral I0 is operably incorporated in the floating roof 12 in storagetank M. A cover It is arranged to protect the mechanism from obstructionby snow and ice. Holes are let into the cover I 6 to give access to theatmosphere and prevent gases from accumulating and interfering with theoperation of the device. In mild climates or seasons, or undercircumstances where the floating roof I2 is not exposed to the elements,the cover It may be omitted, although included here.

A signal release means including a latch bar l8 projecting through thecover It and the release arm as pivotally mounted at 22 on the uppersurface of the float i 2 holds the cable 26 by engaging the ring 2d.These elements indicate a simple means for releasing the liquid levelindicator and transmitting any desired signal as later described.

At a convenient location outside the storage tank M a depth indicator 28is placed. Normally indicators of this type are placed adjacent thestorage tank facing a direction from which they can easily be read. InFigure 1, it has been set away from the storage tank to betterillustrate the cooperative arrangement of the elements. The cable 26 isconnected to the ring release 24 and passes up through the interior ofthe tank H3 over sheaves such as 36 and 32 to reflect movement of thefloating roof I2 on the face of the depth indicator 28. A weightedmarker 34 arranged to show the depth on the indicator 28 is fashioned topresent a regular surface to the foot marks 38 or other indicia for easyreading. This weight 34 may be made of a conducting metal or may besupplied with a conducting band of metal arranged to engage the contacts38 and 49 of the conductors 32 and 44. By such an arrangement, aconventional electric circuit is closed to excite a proper signallingsystem of any desired type and positioned at a selected location. Asmany such signalling devices are known and form part of the presentinvention only as a result of the operation of the disclosed mechanism,they are neither claimed nor illustrated.

A means to cushion the impact of the weight 34 as it is dropped to thebottom of the indicator 2 is shown in the form of a contact support 46,guided by rods 48 and E! positioned in the base 52 and supported bysprings 54 and 5b. The cushioning and contact means should be arrangedto compress within an unmarked or danger indicat ing zone of theindicator depth board 28 below the last indicated depth measurement.Otherwise, to stop it at the last level mark on the board 26 wouldindicate a full and properly operating tank, erroneously.

Figure 2 illustrates the neutral or normal position of the operatingelements included in the float mechanism previously referred to asnumeral It! in describing Figure 1. This figure will be used to describethese elements and their relative positions prior to discussing theoperation of the device. The vented cover it is indicated in thisdisclosed form of the invention as cylindrical in shape. It fits snuglyin an opening made completely throught he floating roof l2 and isexposed to the body of the stored liquid. A latch bar I8 is passedthrough the cover [6 and is supported by bearing surfaces therein asindicated. 0n the end of the latch bar It opposed to the end whichengages the release arm 2%, a spring Si! is compressed between the coveriii and a flange 62 tending to urge the latch bar into engagement withthe release arm. The ring it attached to the cable 26 is retained by thepivoted release arm 20.

Within the cover IS, the operating rod 64 is positioned by the spiderB6. The upper end of this rod 64 is notched as at 58 to cooperate with aslot it in the latch bar l3 shown in Figure 6. Flanges l2 and 14- arespaced on the rod to engage the float 16 as it lifts or drops. The floatit may be made of light metal, solid or hollow, or of impregnated wood,cork, or other like materlal, as required for proper and efficientoperation. Although the cover is vented to permit free passage of air tothe latching mechanism, it af-- fords shelter against freezing andgumming and preserves lubricant or similar coating which assistoperation.

On th lower end of the operating rod 64, a tripod is is fixed. Thistripod forms an extension to engage the bottom of the storage tankshould the roof 12 be permitted to descend below the desired minimumlevel. It will be recognized that this feature may be omitted shouldother means for ascertaining minimum level be presently incorporated ina tank and only the float device be included.

Between the spider 66 and the lower flange l4, spring GE! is mounted onthe operating rod 64. This spring is selected to support the weight ofthe operating member including the rod and tripod, yet is of suflicientflexibility not to interfere with the operation. The weight of thecombined elements is supported to prevent operation of the device exceptwhen required.

Disclosure of the operation of the device requires reference to Figure 1and the group of figures numbered 2 to 5, inclusive. The positions of thseveral elements as indicated. in Fi re 1, 2, 6 show the normaloperation of the floating roof equipment and the visible indication of 4the roof level on the indicating board 28. Continued normal operationwithin the prescribed maximum and minimum levels allowed for the liquidsupported roof will maintain these ele ments in this relative position.

.Eihould the floating roof either reach the maximum elevation permittedin the tank [4 and be stopped as by the sheave 30 or other like means orbe obstructed so that it could not lift within the tank during apumping-in or filling operation, a condition shown in Figure '3 wouldresult. The floating roof i2 is unable to move upward with the risingsurface of the liquid 82 and the float H5 is lifted to engage the upperflange 12. The buoyancy of the liquid moves the float upwardly with suchforce that the operating rod notch 68 is moved out of the slot TE! inthe latch bar it. The lower sloping end of the notch 68 urges the latchbar to further compress the spring fill and releases the arm 20. As theweighted pointer 34 is supported by the cable 26 and the ring 24, shownin Figure 1, the pivoted movement of the release arm 29 frees theweight. The length of the cable 26 is such as to permit the weight 34 todrop to the bottom of the indicator 28 and into the space below thehighest level marking yet not allow the ring to engage the sheave 3D.Springs 54 and 56 prevent injury to the apparatus as the weighted markerdrops and permits completion of the electrical ircuit through the marker34 and the conductors t2 and 44. As noted above this circuit may be usedto ring bells, or operate other Well known signals at any locationdesired.

The operation described in which reference is made to Figure 3 coversthe situation of controlling overflow of floating roof tanks and usesthe float it as the signal actuator. This problem has been recognizedand contact devices above the maximum elevation arranged to meet thisneed. However, the use of the same mechanism to meet all commonemergencies experienced in floating roof tank operation is the purposeof this invention. The operation of the above described device as awarning for the remainder of these common emergencies will be described.

Figure 4 illustrates the situation where the stored liquid is beingpumped out of the tank and the floating roof is stuck and cannot followthe diminishing liquid level. This condition can be met anywhere betweenthe maximum and minimum levels of liquid allowed, and is usually theresult of freezing around the roofs peripheral seal. As the liquid levelWithdraws from support of the roof l2 the float 16 drops down andengages the lower flange 14. Although the float is buoyant and isreadily supported by the liquid 82 because of its shape and specificgravity, it has appreciable weight which is enough to compress thespring 8!) and move the rod @154 downwardly.

In th downward movement, the upper sloping or bevelled face of the notch68 in the operating rod 54 engages the latch bar 18 and urges it awayfrom engagement with the release 23. The operation of freeing theretained cable 26 and resultant dropping of the weight 34 to indicatefailure and complete the electrical warning signal is as alreadydescribed. Again, as in the description of Figure 3, the float "i6 isthe actu" ator.

The final emergency considered in this invention and for which thedisclosed apparatus will also operate is the condition of too muchliquid being withdrawn from the storage tank. In this instance the float16 does not actuate the rod 64 but the extension shown here as thetripod l8 urges the rod to release the latch. Supports are normallyspaced to keep the floating roof level and prevent serious damage to theequipment when more than the allowed quantities of liquid are withdrawnfrom these tanks. Under such conditions there is a hazard of volatileconstituents accumulating beneath the roof in the liquid-vacated space.When this occurs the risk of explosion and fire or both are imminent.Consequently a device which will warn of the downward movement of afloating roof when it has reached the minimum positional depth is verydesirable. Reference to Figure will show the disclosed warning device tobe responsive to this condition as well as the other circumstancesrequiring Warning described above.

As the liquid 82 is withdrawn from the tank M the weighted marker orpointer 34 rises on the indicator 28 to indicate the liquid level.Normally a minimum depth is marked for attention of the operators, butfailure to pump-in at the right time permits the roof 12 to descend tothe bottom of the tank, At the desired minimum 7 level the tripod 78engages the bottom of the tank l4 and lifts the rod v64 without theoperation of the float 1B. The latch bar I8 is moved from engagementwith the release arm 20 as above described and the signal circuit andthe visible position of the Weighted marker 34 show a Warning.

It will be understood that the combination of working elements shownhere may be rearranged and replaced with many equivalent structures andstill be Within the scope of the invention. The primary elements are asimple latch releasable by a float operated rod extended for contact atthe lowest depth arranged to release a warning signal. Levers, rods,gears, and cables readily suggest themselves for the transmission of thefloat and contact rod movement to various forms of latch mechanisms.These elements, together with compressed air, hydraulic devices andelectrical assemblies responsive to the float operated-contact rodmovements indicate a wide range of equivalents for the elements of thiswarning device.

I claim:

1. A signalling device for use with floating roof storage tankscomprising a floating roof having an aperture therethrough into thestored liquid, a vertically movable rod supported in the aperture of thefloating roof and extending therethrough for a determined distance aboveand below said roof, a separate float movable in the aperture andadapted to engage the rod in vertical movement, latching means mountedon the top of the floating roof in operating engagement with the rod,and means to indicate inoperability of the floating roof in response tothe latch release on the vertical movement of said rod.

2'. A signalling device for use with floating roof liquid storage tankscomprising in combination with the floating roof, a latch meansoperatively positioned adjacent an aperture through said floating roof,an operating rod supported to extend through the aperture apredetermined distance below the floating roof and into operatingengagement with the latch means, separate float means positioned toengage and operate the operating rod in response to the elevation of thestored liquid relative to the floating roof, and means to. indicate theposition and operability of the floating roof releasably engaged by saidlatch means.

3. A signalling device for use with a floating roof liquid storage tankcomprising a floating roof having an aperture therethrough opening intothe stored liquid, a covered housing for said aperture, a latchpivotally mounted on the floating roof adjacent the housing covering theaperture therein, a bar slidably mounted in the housing to releasablyengage the latch, an operating rod extending from beneath the floatingroof.

upwardly in the housing to operatively engage the slidable bar, a floatadapted to lift and lower the operating rod in response to the relativeposition of the liquid level and the floating roof, and means toindicate the elevation of the floating roof retained by the latch andreleasable by movement of the operating rod to indicate operatingfailure.

4. The device defined in claim 3 further characterized by the means toindicate elevation and operating failure of the floating roof includinga graduated member in vertical position adjacent the storage tank andmarked with suitable measuring divisions, a marker slidably movablealong the length thereof, a cable connecting said marker with the latch,and an alarm circuit at the bottom of said indicator electricallyoperated when engaged by the marker.

5. A signalling device for use with floating roof liquid storage tanks,comprising the combination with the floating roof, of a housing in-.serted in an orifice in the roof and in fixed rela- }tion therewith, anoperating rod connected with said roof and extending from below saidorifice into said housing and having a limited vertical movementrelative to the roof, a separate float means positioned to float on thetank liquid when the same is at normal or above normal level and free tofall when the liquid is below normal level, said rod being operable bysaid float member in the movement of the latter a predetermined distanceabove or below the position it occupies when the tank liquid is atnormal level, a lever mounted on the floating roof, latch mechanismcontrolled by the rod to normally hold said lever in latched positionbut movable upon the rise or fall of the rod to unlatch said lever, andsignalling means connected to, and held inoperative by, said lever whenthe same is in latched position but operable when the lever is unlatchedas specified.

References Cited in the flle of this patent UNITED STATES PATENTS NumberName Date 354,508 Fraleigh Dec. 14, 1886 530,659 Schaefler Dec. 11, 1894FOREIGN PATENTS Number Country Date 667,829 France June 25, 1929

